The report sums up a year-long investigation of NHTSA's investigative practices that was requested at the behest of Sen. John McCain (R-AZ). McCain called for the review after Congressional hearings about the Firestone tire tread separation debacle in 2000.
The inspector general's report found that NHTSA often uses incomplete and "flawed" data to decide whether or not to open a vehicle defect investigation. The report found that, in some cases, NHTSA declined to open vehicle defect investigations despite reports of serious injuries, while initiating reviews in defect cases that did not involve any injuries.
NHTSA has agreed to change its investigative practices in response to the report, such as developing new methods to detect and analyze vehicle defects and formulating a better decision-making process to govern whether an investigation is opened or not.